1. Field of the Invention
The present invention relates to novel active alumina agglomerates, to a process for the production of these novel agglomerates and to a particular apparatus for carrying out such process.
This invention especially relates to the hydrothermal treatment of active alumina agglomerates.
2. Description of the Prior Art
Certain catalytic processes, such as heterogeneous catalysis, for example in the field of the treatment of crude oil fractions or the treatment of gaseous effluents, such as the exhaust gases emanating from internal combustion engines, require the use of catalyst supports having a high porosity, good mechanical properties, such as a high crushing strength and notable resistance to attrition.
Supports made of active alumina basically satisfy these requirements, especially after they have been hydrothermally treated. This treatment appreciably improves the mechanical properties of the resulting agglomerates.
Such hydrothermal treatment is known to this art and is described, for example, in FR 1,386,364, 1,449,904 and 2,496,631 and U.S. Pat. Nos. 3,628,914 and 3,480,389.
This hydrothermal treatment entails impregnating starting material alumina agglomerates with water or an aqueous acid solution, then heating the impregnated agglomerates in an autoclave to a temperature higher than 80.degree. C.
The agglomerates treated in this manner are then dried and subjected to a heat treatment, or calcination, at a given temperature. This calcination temperature is selected as a function of the particular specific surface desired and the temperature of actual intended use of the supports.